The Media Development Authority (MDA) forced SingTel to share its English Premier League (EPL) broadcasts because the telco had made it "commercially unviable" for rival StarHub to purchase the rights.
This was revealed for the first time in a document that the MDA put up on its website to explain its decision.
The regulator said that there were two clauses in SingTel's deal with the Premier League which had the "combined effect" of making it exclusive, triggering the cross-carriage rule.
One clause meant that StarHub would not be allowed to announce the purchase of the EPL television rights or promote the matches before a prescribed time. SingTel was also to be told when its rival was set to begin marketing activities with regards to the EPL.
MDA found that this had "a negative impact on consumer knowledge and choice". For instance, StarHub could have lost prospective customers to SingTel between the time that it captured the rights to the EPL and when it was allowed to publicise this.
The other clause said SingTel was entitled to "a significant price reduction" of the fees it paid for the EPL rights. While the rebate size was not revealed, MDA noted this would probably lead to the Premier League asking StarHub for a similar sum for the rights.
That cut the chances of a deal, especially if StarHub did not value the rights so highly.
After SingTel announced last December that it had secured the next three EPL seasons in what was supposedly a "non-exclusive" deal, StarHub complained it was unable to start negotiations for its own rights until March.
In April, MDA ordered SingTel to make available its EPL content on StarHub's pay-TV platform.
This meant that StarHub subscribers did not have to install a mioTV set-top box to watch England's top football league, which kicked off in August. Still, they have to pay the bills to SingTel.
When contacted, a SingTel spokesman said it acknowledged MDA's decision but that it has a different opinion.
"Our intention was never to acquire the rights exclusively," she said. "This is why we lodged an appeal, which unfortunately was turned down."
Senior analyst Clement Teo from research company Forrester said that MDA made a fair call.
"Time is needed to secure sponsors and market to consumers. A delay would reduce a potential revenue window," said Mr Teo.
The cross-carriage rule was mooted about three years ago to stop the problems that came from pay-TV operators hogging exclusive content to boost subscriber numbers.
At the time, SingTel had just wrested exclusive rights to screen EPL matches from StarHub for three years. SingTel reportedly paid $400 million - more than three times what StarHub paid in the previous cycle.
Fans on StarHub's platform, which had more than 500,000 subscribers, were upset at having to subscribe to SingTel's mioTV service for their football fix.
MDA introduced the cross- carriage rule in 2011 to prevent consumers from having to switch to or add another pay-TV operator because it had secured a monopoly on certain content.